The Battle of Britain, The Blitz and the Air War over Britain afterwards...

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Tuesday, March 10, 2015

World War II - Churchill's Aerial Mines Project

The Harrow served in a novel operational role at the height
of the German night Blitz against Britain in the winter of
1940-1941, with six Harrows equipping No. 420 Flight RAF (later to
become No. 93 Squadron RAF) which used lone Harrows to tow Long
Aerial Mines (LAM) into the path of enemy bombers. The LAM was an
explosive charge on the end of a long cable. This unorthodox tactic
was credited with the destruction of six German Bombers or 4-5,
depending on the source. The experiment was however judged of poor
value and the planned deployment of Douglas Havocs in the LAM role
cancelled.

The Harrow served in a
novel operational role at the height of the German night Blitz against Britain
in the winter of 1940-1941, with six Harrows equipping No. 420 Flight RAF
(later to become No. 93 Squadron RAF) which used lone Harrows to tow Long
Aerial Mines (LAM) into the path of enemy bombers. The LAM was an explosive
charge on the end of a long cable. This unorthodox tactic was credited with the
destruction of six German Bombers or 4-5, depending on the source. The
experiment was however judged of poor value and the planned deployment of
Douglas Havocs in the LAM role cancelled.

No. 420 Flight formed on 29th September 1940, under the
command of Flt. Lt. Burke for the purpose of experimental work in connection
with the use of aerial mines in intercepting enemy planes.These experiments were carried out with
Harrow aircraft using Battle aircraft as targets.On 26th October, the first practical
experiment took place against the enemy, one aircraft being probably destroyed.

On 7th December, 1940 this Flight became No. 93 Squadron
under the command of Wing Commander J.W. Homer.It consisted of 2 Havoc Flights and 1 Wellington Flight. Experiments
continued and on 23rd April 1941 the 2 Havoc Flights became operational on
night interception duties using mines and the third flight was taken to form
the Fighter Experimental Establishment.

Wing Commander M. B. Hamilton assumed Command on 23rd April,
1941.

During the following months the Squadron flew numerous
operational sorties from Middle Wallop with detachments operating at various
times from Coltishall, Hibaldston and Exeter.There is no record of any enemy aircraft destroyed during this period
and towards the end of the summer few operational sorties could be made owing
to (i) the absence of enemy aircraft and (ii) the presence of friendly
aircraft.

At the end of November a decision was taken to discontinue
the use of aerial mines in night interception and as a result of this decision
No. 93 Squadron was disbanded on 6th December, 1941.

The Long Aerial Mine
(LAM)

This entered service towards the end of 1940. The background
to this weapon is interesting.Before
the war, tactical papers had often exaggerated the danger to conventional
fighters of attacking bomber formations. It was argued that the defensive
crossfire from 20 or more bombers in close formation might inflict heavy losses
on the interceptors.

Therefore it was important to devise a method of breaking-up
bomber formations, to allow the fighters to pick off the bombers
individually.One proposed method was
to lay a defensive minefield.A line of
such mines, positioned across the path of an enemy bomber formation, would
certainly cause it to break up.

Following much experimentation, the optimum configuration
for the mine was determined. The resulting weapon fitted into a cylindrical
container 14in long and 7in in diameter, and weighed 141b.After release from the aircraft the obstacle
deployed. It comprised, from top to bottom: a supporting parachute, a length of
shock-absorber cord, the cylindrical container, an AAD bomb, 2,000ft of piano
wire and, at the bottom, a second furled parachute.

When an aircraft struck the piano wire the shock wave ran up
the wire, causing a weak link to break, releasing the main supporting parachute
and the cylindrical container. As the container fell away the bomb was armed
and a small stabilising parachute connected to the weapon was released.Simultaneously, the shockwave travelled down
the piano wire and caused the lower parachute to open.This took up a position behind the aircraft
and pulled the bomb smartly down on the aircraft.

In the event, the Long Aerial Mine (LAM) was not ready for
operations in time for the Battle of Britain.However, in autumn 1940 Fighter Command's most difficult problem became
how to counter the night raider.The
long-term answer was the Bristol Beaufighter fitted with airborne interception
(AI) radar, directed on to its prey by a ground-controlled interception (GCI)
precision radar.But each of those
systems was in an early state of development, and some time would elapse before
they were available in quantity. In the meantime, anything even remotely likely
to be effective against the night bombers was pressed into use, including the
Long Aerial Mine.German bombers
attacking at night did not fly in formation.Instead, they approached their targets at irregular intervals, following
their radio beams.At night, the mines
were to serve a different purpose than that originally proposed.Instead of being used to split up an enemy
formation, a line of mines would serve as an "aircraft trap" to
destroy bombers.

The minelaying task did not require an aircraft with
particularly high performance. The machine selected was the obsolete Handley
Page Harrow twin-engined bomber. Fully laden, its maximum speed was 170 m.p.h.
at 20,000ft, and it took all of 46 min to reach that altitude.The Harrow was modified to carry 120 Long
Aerial Mines weighing nearly 1,7001b.For night operations the spacing between individual mines was 200ft, so
the Harrow's complement would produce a curtain of danger 4½ miles long and
2,000ft deep.The individual mines
descended at about 1,000ft/min, so the curtain remained effective for about 2
min.

In September 1940 No 420 Flight formed at Middle Wallop with
modified Harrows. During December the Flight was expanded into 93 Sqn and the
new weapon was sent into action.For
these operations the Harrow was guided by ground radar to a release position in
front of the raiders.On the night of
December 22, Fit Lt P.L. Burke laid out a line of mines in front of two enemy
bombers.Shortly afterwards one of the
radar "blips" seemed suddenly to disappear from the screen, and the
bomber was assessed as "probably destroyed".

One of those who flew Harrows with 93 Sqn during the Long
Aerial Mine operations was Flt Lt Dennis Hayley-Bell.He later told the writer:

"One flew alone in the Harrow, which meant that during
the long climb to height and the subsequent wait for the enemy one felt rather
lonely.The clumsy Harrow was not an
ideal machine to go to war in.It was
very slow and, because there was no heating and the cockpit sealing was often
poor, very cold at high altitude.When
the radar controller saw a likely-looking enemy bomber coming in my direction,
he would direct me on to an intercept heading to one side and about 1,000ft
above the intended victim. At the critical moment I would receive the order to
turn sharp left or right, so as to bring me across the path of the victim.Then I would start the 'Mickey Mouse' the
clockwork unit which released the bombs - at the correct time intervals (just
under 1 sec) so they were strung out at 200ft intervals behind the
aircraft.It took about 1½min to drop
one's complement of mines, then it was just a question of waiting.If one was very lucky, one might see a flash
to indicate that an enemy aircraft had hit one of the wires and dragged down
the bomb.But usually there was nothing
to be seen.The mines were always released
some way out to sea, because any coming down on land might cause damage. During one of the early operations the ground
controller failed to make sufficient allowance for the wind, with the result
that several mines landed near Bournemouth and the long wires shorted out
overhead power lines in the area. Fortunately everyone blamed the resultant
power cuts on the Germans, so we escaped any awkward questions."

Hayley-Bell's only successful mining operation was on the
evening of March 13, 1941, as German bombers came across the coast to attack
Liverpool, Hull and Glasgow. After taking off from Middle Wallop in a Harrow,
he climbed to 17,000ft.Directed by the
radar station at Sopley, near Christchurch, he was positioned about four miles
ahead of and 3,000ft above an incoming bomber.At a point 12 miles off the coast near Swanage he was ordered to begin
releasing the mines.After a short wait
he saw a small explosion below him, followed by a much larger detonation,
powerful enough to shake the Harrow.Radar operators on the ground observed that the intended victim had
missed the minefield, but it appeared that another bomber in the area had
picked up a mine.Hayley-Bell was
credited with one enemy aircraft destroyed.

Between March 11 and July 29, 1941, 93 Sqn flew a total of
112 minelaying sorties, and in the course of these its aircraft attempted 59
interceptions.Of those, only 16 were
sufficiently promising to warrant the laying of a minefield.The outcome was one enemy bomber
(Hayley-Bell's) claimed "destroyed" and three more "probably
destroyed".

During the summer of 1941 the German night raids tapered
off, and by then the Beaufighter was in service in useful numbers.Compared with that, the Long Aerial Mine
gave only a very low probability of a kill, and operations with the weapon
ceased in October 1941.

1 comment:

Hi Mitch, Very interesting article. I am writing my PhD on the impact of the Second World War on piano manufacturing in Britain and I would like to use your image of the LAM drawing. Can you share where you found it? Thanks, Sarah